1. Field of the Invention
The present invention relates to a print processing system and method which produce printed output by processing the print information described in print languages, such as page-description languages, using a plurality of image forming units.
2. Description of the Related Art
As development of a print system suitable for use in high-speed digital printing operations such as electrophotography or ink-jet printing operations, a print control scheme that breaks from conventional textual-information-oriented printing, that deals with images, graphics, characters, or the like, in the same manner, and that uses "page-description languages" capable of freely controlling the enlargement, reduction, rotation, and deformation of characters or graphics has achieved widespread use. Various page-description languages were developed during the 1980s. PostScript (a registered trademark of Adobe Systems in U.S.) and Interpress (a registered trademark of Xerox Corporation in U.S.) are representatives of the page-description languages. Various printers employ many page-description languages.
In a conventional page-description language processing print system, the central processing unit (CPU) of the print system sequentially interprets a page-description language, whereby a printer of the print system executes a printing operation. One example of the conventional page-description language processing print systems is disclosed in Unexamined Japanese Patent Application No. Hei 1-188374. The conventional page-description language processing print system is provided with a storage device that receives and stores a program for printing purposes (hereinafter referred to as print information) fed from a computer (hereinafter referred to as a host computer), a processor for sequentially interpreting that information, and a printing apparatus for executing a printing operation according to the thus-interpreted print information. After the print information has been transmitted from the host computer to the printing apparatus, the printing apparatus translates the print information and carries out a printing operation, whereby the load on the host computer is relieved. In consequence, the possessing speed of the overall print system is improved.
The sharing of a printing apparatus is standard practice in a decentralized network environment. Such a printing apparatus receives print requests from many host computers and must interpret and execute the print information described in a page-description language. Where many host computers concurrently use that printing apparatus, the printing apparatus serially interprets and executes the print information described in the page-description language, which results in a longer wait time elapsing between requesting and receiving print output.
To solve the foregoing problem and process print information at high speed, several techniques have been proposed: for example, a multiprocessing print processing system (see, e.g., Unexamined Japanese Patent Application No. Hei 4-128068) that interprets and executes print information in a parallel manner by use of a plurality of processors which are tightly coupled through a bus, or a print processing system (see, e.g., U.S. Pat. No. 5,333,246) that interprets and executes print information in a parallel manner by means of a decentralized network consisting of a plurality of loosely-coupled processors.
In the print processing system disclosed in Unexamined Japanese Patent Application No. Hei 4-128068, a special processing is not carried out with regard to the division of print information in order to interpret and execute the print information in a parallel manner. The print information is simply split page by page. In the case of the print information whose print job consists of a plurality of pages, a processing time is reduced. However, in the case of the print information whose print comprises only one page, the effect of reducing the processing time is not achieved.
In the print processing system disclosed in U.S. Pat. No. 5,333,246, the overlap between images is detected with regard to the division of the print information in order to interpret and execute the print information in a parallel manner. The print information is split on "an image group basis which does not affect another image even if that image group is separated from the print information". The thus-split print information is subjected to parallel processing. In this case, even in the case of the print information whose print job consists of one page, the effect of reducing the processing time is achieved. Since the processing is executed on a split-image group basis, the time required to carry out the processing will become a bottleneck if some of the plurality of split image groups are very complicated, for example, if they comprise overlapping images. As a result, the processing time of the entire page is not frequently reduced.
Neither the technique disclosed in Unexamined Japanese Patent Publication No. Hei 4-128068 nor the technique disclosed in U.S. Pat. No. 5,333,246 takes into consideration the efficient arrangement of the resources necessary for the print information. Specifically, in the case where the processing of print information is shared between the plurality of print information processing apparatuses, many print processing apparatuses respectively hold the resource information required to carry out raster graphics processing of the print information such as font information. The holding of the same resource information of the print processing apparatuses in an overlapped manner results in considerable overhead in the print processing system, as is the case of memory locations, processing costs, and transmission costs. In an extreme case, as a result of the overhead, the parallel processing carried out by a plurality of print information processing apparatuses may become inferior to the ordinary processing carried out by a single print information processing apparatus. For this reason, the effect resulting from high-speed parallel processing will not be achieved unless the efficient arrangement of the resources required to print the print information is not taken into consideration.